By Steve Holland and Emily Stephenson | WASHINGTON President Donald Trump’s national security adviser, Michael Flynn, resigned late on Monday under scrutiny over whether he discussed the possibility of lifting U.S. sanctions on Russia before Trump took office. Flynn submitted his resignation hours after Trump said through a spokesman that he was reviewing the situation and talking to Vice President Mike Pence. Flynn had promised Pence he had not discussed sanctions with the Russians but it was later discovered that the subject had come up. “Unfortunately, because of the fast pace of events, I inadvertently briefed the vice president-elect and…